Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on efficiencies associated with well completions and maintenance over the life of the well. By the same token, offshore wells along with those of ever increasing depths and sophisticated architecture have emerged. Thus, added levels of complexity in terms of completions and maintenance have become fairly commonplace.
In terms of basic architecture, the terminal end of a cased well often extends into an open-hole lateral leg section. Such architecture may enhance access to the reservoir. At the same time, however, this basic architecture presents certain challenges when it comes to their completions and maintenance. For example, a variety of hardware may be installed near and above the lateral leg before production through the leg is commenced. Additionally, perforating, fracturing, gravel packing and a host of other applications may be directed at the leg in advance of production.
In order to carry out the different completions tasks, a formation isolation valve may be present at the juncture between the noted leg and cased regions thereabove. This valve may help to ensure a separation between completion and production fluids. More specifically, comparatively heavier fluids utilized during completions may be prone to adversely affect the formation if allowed to freely flow to the production region of the leg. By the same token, production of lighter high pressure fluids into the main bore during hardware installations may adversely affect such operations. By way of a more specific example, the leg may be outfitted with a formation isolation valve that is opened for gravel packing and other early stage leg applications. However, such a valve may be subsequently closed to isolate the open-hole portion of the leg as other completions tasks are carried out uphole of the leg.
As indicated, closing the valve may avoid fluid loss during completions operations and also maintain well control in the sense of avoiding premature production of well fluids. This closure may be achieved in conjunction with removal of application tools from the open-hole region of the leg. So, for example, following a gravel packing application in a lateral leg, a shifting device incorporated into the gravel packing wash pipe may be used to close off the valve as the assembly is removed from the area. Thus, completion of the application and retrieval of the tool involved may be sufficient to close the formation isolation valve.
Unfortunately, in certain circumstances, the valve may become stuck, thus, preventing retrieval of the tool and assembly as described above. Thus, continued pull on the assembly could potentially result in a breakage that might lead to a host of complications ranging from tool damage to expenses and delays associated with follow-on retrieval operations. Therefore, to avoid such complications, the shifting tool is generally configured with emergency release capacity as noted below.
The valve shifting tool works to shift open the formation isolation valve by interlocking engagement with a matching profile of the valve. More specifically, the tool engages a mandrel of the valve such that upon removal of the assembly, the mandrel is pulled uphole so as to close the valve. However, the engagement portion of the tool is configured for emergency release as noted above for circumstances where the valve has become stuck. So, for example, once a predetermined amount of uphole force has been exerted, and yet the mandrel remains stuck in place, the engagement portion of the tool may deflect out of engagement with the mandrel. More specifically, where 2,000 lbs. to 5,000 lbs. of force has been exceeded without mandrel shifting, the noted deflection will occur and the assembly will be safely removed from the well. In this manner, the tool may be retrieved from the valve and visually assessed at surface for any damage during the emergency release. However, as detailed further below, no such visual inspection or quick remedy is available for assessment and/or repair of the valve which is disposed far downhole.
As indicated, the described deflection and removal of the assembly avoids complications that might otherwise result from a broken tool. Unfortunately, however, this deflection and removal of the assembly still leaves an open formation isolation valve at the junction of the cased and open-hole well regions. Thus, for all intents and purposes the valve fails to achieve its intended use in terms of isolation. Further, as the typical emergency release process is likely to result in damage to the valve, it must be assumed that the valve is damaged such that typical work over remedies (e.g. flushing or circulating fluid to remove debris) will be ineffective in remedying the valve state. As a result, this means that another set of complications is now introduced. Namely, costly delays and expenses associated with the introduction of alternate interventions directed at the valve or new isolation techniques to compensate for valve failure will now likely be introduced.
Once more, even though the tool, in theory, may be constructed of materials capable of withstanding load pull far in excess of 5,000 lbs., deflection is generally set to take place at such relatively low thresholds. This is due to the fact that the engagement between the tool and the mandrel is of a multi-member or ‘collet’ variety which can result in a substantially uneven distribution of radial forces during the singularly upward pull. Therefore, as a practical matter, lower thresholds are presently required to prevent breakage of any individual collet member where such a deflection technique is employed for the emergency release. Therefore, as a practical matter, lower thresholds are presently required to prevent breakage or significant damage of any individual tool collet member where such a deflection technique is employed for the emergency release. This is particularly the case in light of added concerns over the effect such breakage may have on the valve as well.